Persons with partial and total walking disabilities have traditionally relied upon wheel chairs for locomotion. Wheel chairs generally have relatively widely spaced wheels for lateral stability and to comfortably accommodate the occupant. Persons in wheel chairs can move with relative ease in places such as hospitals which are usually provided with extra wide doors and halls and inclined ramps between vertically displaced levels. However, private homes and work places are generally not planned specifically to accommodate wheel chairs. While wheel chairs are generally resistant to lateral tipping they are often designed for tipping backwards so that an attendant pushing a patient in a wheel chair can tip the front wheels up to negotiate obstacles such as steps, thresholds and the like. While such a configuration is useful when the wheel chair is pushed by an attendant, the design presents some hazards when the wheel chair occupant attempts to wheel himself up a ramp. Further, there is a degree of social stigma attached to wheel chairs such that wheel chair occupants are sometimes shunned as "handicapped".
In order to overcome some of the problems associated with wheel chairs, the medical equipment industry has developed small personal mobility vehicles as an alternative. Such vehicles generally have a pair of rear wheels, a steerable front wheel, are powered, and in general have the appearance of a down sized golf cart. The track of the rear wheels is generally narrower than that of wheel chairs, the wheel base is generally longer, and the vehicles are generally designed for tight turning radii such that the vehicles are more maneuverable than wheel chairs and therefore, more useful in places which are not specifically designed for wheel chair use.
Because such personal mobility vehicles generally require a narrow wheel track to pass through doorways of normal width, and also utilize a generally short wheel base for ease of maneuverability in tight turning radii, the vehicle may lack stability and be easy to roll over to one side with the resulting of injury to the operator. One known vehicle, in order to overcome such maneuverability and stability problems employs an expansible rear wheel mechanism for controlling the length of the vehicle between the wheel base, and for widening and narrowing the wheel track. This mechanism is entirely hand operated and requires the user to lift the rear of the vehicle up, remove pins and slide in or out telescoping shafts on which the axles are mounted. This is generally unsatisfactory because such vehicles are often used by the aged or otherwise infirm who may not have the required strength to accomplish the task. Because the mechanism of changing the wheel base and wheel track is manual and requires stopping and manipulating components, the user usually elects to forego such adjustments and maintains the vehicle in a narrow track, short wheel base configuration in order to make sharp turns and maneuver through doorways. Consequently, any advantage of the expansible wheel base and wheel track mechanism is lost because of the difficulty of use.